a. Field of Invention
The invention relates generally to electric powered wheelchairs, and, more particularly to an apparatus and method for customized control of an electric powered wheelchair.
b. Description of Related Art
Position sensing devices are integral components of computing systems, the ubiquitous “mouse” being one of the best examples. Joysticks are also common, and find applications in computer games, medical devices, wheelchairs, robotics, aircraft, advanced vehicles, and other devices. Other examples of position sensing devices include trackballs and virtual reality equipment such as helmets, goggles, gloves, and foot pedals. The earliest joysticks were basically a simple arrangement of contact switches at four quadrants. Moving the joystick shaft away from its centered position closed one of the four switches, depending on the direction of movement. Springs connected to the joystick returned the device to a central position when the joystick was released. The resistance to motion, called compliance, that is provided by the springs could be provided or augmented by other means, such as having the joystick move through a viscous fluid.
An improvement to the contact switch joystick was made by development of the position sensing joystick. In this arrangement, the joystick was coupled to two potentiometers mounted at right angles. Motion of the joystick produced voltages from the potentiometers that indicated the position of the joystick. Later variations of position sensing joysticks employed optical encoders to determine the joystick position, replacing potentiometers. Further refinements of position sensing joysticks included the addition of tactile and force feedback. Tactile feedback is a simple vibration generated when provided position information falls within some desired region. Force feedback devices actually apply forces to the joystick shaft, for example, pushing against the operator induced motion. Force feedback may be used to indicate to a robotic operator that contact with an object has been made. The force sensing, or isometric, joystick used strain gauges to measure forces applied to the joystick with no motion of the joystick required. An example of such a joystick is the miniature isometric joystick used on laptop computer keyboards.
In view of the aforementioned developments, today's electric powered wheelchairs include several components for facilitating control of movement thereof, including proportional position sensing joysticks, electric powered wheelchair controllers, isometric joysticks, damped joystick controls, joysticks with corrective algorithms and integrated control features, and wheelchair driving simulators.
Proportional position sensing joysticks for electric powered wheelchairs are known in the art and generally allow individuals with impaired mobility to drive such wheelchairs. Position sensing joysticks produce speed and direction signals proportional to the joystick's directionality and angle of deflection. It has been shown that such joysticks are inadequate for as many as 40% of potential wheelchair users, partly because they are built on a “one size fits all” philosophy. For example, current clinical practice is to have a user try out various commercially available position sensing joystick controls, and then select a handle and mounting position most compatible with the user's residual hand function. Frequently, none of the commercial position sensing joystick controls are suitable and the user is often downgraded to single switch head arrays rather than a proportional control system. While single switch technology can be operated with limited and imprecise limb movement, the result is generally a slow and awkward wheelchair control system.
With regard to electric powered wheelchair controllers, such controllers generally include a power regulating circuit between the position sensing joystick and the wheelchair drive motors. Controllers translate the speed and direction signals from the user control (i.e. a joystick) into appropriate current levels that are applied to the drive motors of a wheelchair. Over the years, the improvement and perfection of such controllers has been a focus of the wheelchair industry. Early controllers generally included simple driving algorithms, an example of which includes a controller operated by a driver pushing a position sensing joystick to the right or left, at which time the controller decided whether to merely slow the wheel inside the turn or, in the event of a sharp, low speed turn, to run the inside wheel in reverse to produce a tighter turning circle. In more modern controllers, in order to safely match an electric powered wheelchair to different driving abilities of particular users, manufacturers provide several adjustments on their controllers that a vendor or clinician may set with a hand held programmer. An exemplary adjustment may include adjustment of the maximum velocity the wheelchair will achieve during straight ahead or turning maneuvers. Modern controllers also include advanced algorithms to stabilize a wheelchair in hazardous terrain, such as during climbing or descending steep grades, or when traversing a cross slope. Even in light of the aforementioned improvements in controllers, commercial controllers and position sensing joysticks are generally unable to recognize or in any way correct for an operator's unintentional hand movements. Another major disadvantage of currently available controllers is that they only serve the electric powered wheelchair, and do not support the control of any other associated device, such as personal computers or environmental control systems.
With regard to isometric joysticks, as discussed above, such joysticks are generally used with personal computers. A well-known example of an isometric joystick includes the “eraser head” mouse used on many laptop computers. While such joysticks are known in the industry, these joysticks have had limited application in the field of electric powered wheelchairs due to the associated limitations in the ability of user to adequately operate the joystick.
With regard to damped joystick control, while such a control methodology is known in the industry, damped control for joysticks has generally been used in the reduction of hand tremor. Moreover, the damped control methodology has primarily been used for position sensing, and not for control of electric powered wheelchairs.
Lastly, with regard to wheelchair driving simulators, while simulators have indeed found applications in the automotive field, as with automobile driving simulators, for example, such simulators are however not applicable to wheelchair driving. Moreover, no known driving simulators have been used to tune electric powered wheelchairs or associated joysticks.
Accordingly, there remains a need for a customizable and versatile control technology for electric powered wheelchairs. There also remains a need for a variable compliance joystick for electric powered wheelchair control and for facilitating the customization of the aforementioned technologies for users with various disabilities.